P1638 throttle stuck what happens is that some debris got on the throttle body near the throttle plate. The throttle plate motor is drawing more current from the computer than it's designed to. It is drawing more current than needed to move the throttle plate. It's not designed to move debris or gunk if it encounters an obstruction and can't close for a few milliseconds it will throw the code.
I had this problem on my R56 MINI Cooper. What I did was use some lubricant spray oil into the pipe that connects to the throttle body to the valve cover. Then start the engine at idle and spray a few sprays of that lube into the PCV until you hear the engine rev up a little. Then put pipe back on and rev your engine a few tines so the throttle plate moves around a little bit. Then do this over again one time, then clear the code using scan tool code should not come back.
If it comes back then you need to do this again a few times or turn car off disconnect battery and take off the air hose to throttle and spray lube oil directly on throttle plate and body. While at it, clean with a rag then re-assemble. Start car also, then turn car off and unplug MAF. Then plug back in the connector to make sure it's secure. Start car and code should not return.